TY  - THES
AB  - Antimalarials are drugs used against malaria, an infectious disease caused by a parasite that belongs to the genius plasmodium. Drug therapy to eradicate this disease is increasingly hindered by resistance of the parasite to drugs currently in use. The drug resistance has been partly attributed to the presence of drugs with wrong or low active pharmaceutical ingredients. Thus, there is an increasing need for analytical procedures to investigate the quality of antimalarial-based pharmaceuticals. Amongst the analytical techniques, the most used to date is high performance liquid chromatography (HPLC) in the reversed-phase (RP) mode coupled to mass spectrometry (MS). However, RP-HPLC is characterised by a relatively long analysis time and a consumption of a large amount of organic solvents. In a quest to develop a fast and efficient analytical method, different mass spectrometric-based techniques are developed and optimised in this thesis. In the first section, high-temperature HPLC mass spectrometry (HT-HPLC-MS)-based technique tailored for the analysis of antimalarials is developed and optimised. HPLC at high temperature permits faster separation compared to standard conditions with a reduction in chemical waste, better chromatographic selectivity and an enhanced desolvation in the MS ionisation source. Prior to HT-HPLC-MS method development, a HT-HPLC heating system was optimised for best performance and successfully coupled to a triple quadrupole mass spectrometer via electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APCI) sources. Because of the antimalarial properties of Cinchona alkaloids, a HT-HPLC-MS method with an XBridge C18 column and ESI source was developed and optimised for their analysis. The optimised method permits the separation and detection of the four major chiral alkaloids: cinchonine, cinchonidine, quinine, and quinidine and their dihydro-derivatives: dihydrocinchonine, dihydrocinchonidine, dihydroquinine, and dihydroquinidine with reduction in analysis time and organic solvents, better chromatographic selectivity and enhanced MS ionisation efficiency. Limits of detection (LOD) in the µg L-1 range were obtained. The method was shown to be suitable in the separation and detection of Cinchona alkaloids present in a commercial sample. Also, because of the antimalarial properties of artemisinin (ART) and some of its derivatives (artesunate (AS), dihydroartemisinin (DHA), and artemether (AM)), another HT-HPLC-MS strategy with a zirconia-polybutadiene (ZrO2-PBD) column, was developed and optimised for their analysis. After optimisation, DHA, ART, and AM were detected as their ammonium adducts ([M + NH4]+) at m/z 302, 300, and 316, while AS was detected as a characteristic fragment ion at m/z 272. From evaluation of ESI and APCI sources during HT-HPLC-MS analysis, best detection sensitivity for ART and derivatives is obtained with ESI compared to APCI. LODs in the µg mL-1 range were obtained with HT-HPLC-ESI-MS. The optimised HT-HPLC-ESI-MS and HT-HPLC-ESI-MS/MS method were successfully applied in the screening of AM in commercial Coartem drug tablets.
In the second section, direct MS-based methods, which use minimal sample preparation procedures and relatively small sample amounts were developed and optimised for fast screening of antimalarials. In the first part of this section, a time-of-flight secondary ion mass spectrometry (ToF-SIMS) method was optimised to screen for Cinchona alkaloids including quinine (Qn). ToF-SIMS analysis of Qn provided significant fingerprint SIMS fragments, which were later used in the fast qualitative screening of Qn and related compounds in small amounts of Cinchona bark and extract. The results demonstrate for the first time the ability of ToF-SIMS to perform direct analysis and fast qualitative screening (less than 10 minutes analysis time) of Cinchona alkaloids. In the second part of this section, an analytical method involving low-temperature plasma ambient desorption/ionisation mass spectrometry (LTP-ADI-MS) was developed and optimised for rapid qualitative screening of active antimalarial pharmaceutical ingredients. The method was shown to be capable of detecting the active ingredient in antimalarial drug tablets (Coartem and Malarone) as their protonated molecular ions and other characteristic ions in less than three minutes and with minimal sample preparation. Characteristic fragment ions of target molecules were used for structural identification even in the presence of a tablet matrix.
AU  - Ateacha, Derick Nzogoa
DA  - 2018
KW  - Massenspektrometrie
KW  - Hochtemperatur-HPLC
KW  - Antimalaria-Arzneimittel
KW  - Direkte MS-Analyse
KW  - Mass spectrometry
KW  - High-temperature HPLC
KW  - Antimalarial pharmaceuticals
KW  - Direct MS analysis
LA  - eng
PY  - 2018
TI  - Development and optimisation of mass spectrometric techniques for the analysis of antimalarial pharmaceuticals
UR  - https://nbn-resolving.org/urn:nbn:de:hbz:467-13401
Y2  - 2024-11-22T09:26:14
ER  -